Textural changes in metallurgical coke prepared with polyethylene

The effect of high-density polyethylene (HDPE) on the textural features of experimental coke was investigated using polarized-light optical microscopy and wavelet-based image analysis. Metallurgical coke samples were prepared in a laboratory-scale furnace with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% HDPE by mass, and one sample was prepared by 100% coal. The amounts and distribution of textures (isotropic, mosaic and banded) and pores were obtained. The calculations reveal that the addition of HDPE results in a decrease of mosaic texture and an increase of isotropic texture. Ethylene formed from the decomposition of HDPE is considered as a probable reason for the texture modifications. The approach used in this study can be applied to indirect evaluation for the reactivity and strength of coke.     

高炉焦石墨化过程中孔隙结构的演变

Pore structure is an important factor influencing coke strength, while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace. Therefore, an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace. Coke graphitization was simulated at different heating temperatures from 1100 to 1600°C at intervals of 100°C. The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method. Results show that the adsorption and desorption curves of graphitized coke have intersection points, and the two curves did not coincide, instead forming a “hysteresis loop.” Based on the hysteresis loop analysis, the porous structure of the graphitized coke mostly appeared in the shape of a “hair follicle.” Furthermore, with an increase in heating temperature, the apparent porosity, specific surface area, total pore volume, and amount of micropores showed good correlation and can divided into three stages: 1100–1200, 1200–1400, and 1400–1600°C. When the temperature was less than 1400°C, ash migration from the inner part mainly led to changes in the coke pore structure. When the temperature was greater than 1400°C, the pore structure evolution was mainly affected by the coke graphitization degree. The results of scanning electron microscopy, energy dispersive spectrometry, and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400°C contributed to these changes.     

Precipitation analysis of as-cast HK40 steel after isothermal aging

As-cast HK40 steel was aged at 700, 800, or 900℃ for times as long as 2000 h. Microstructural characterization showed that the primary M₇C₃ carbide network contained a substantial content of manganese, in agreement with the microsegregation of manganese calculated by Thermo-Calc using the Scheil-Gulliver module. The dissolution of primary carbides caused the solute supersaturation of austenite and subsequent precipitation of fine M₂₃C₆ carbides in the austenite matrix for aged specimens. During prolonged aging, the carbide size increased with increasing time because of the coarsening process. A time-temperature-precipitation diagram for M₂₃C₆ carbides was calculated using the Thermo-Calc PRISMA software; this diagram showed good agreement with the experimental growth kinetics of precipitation. The fine carbide precipitation caused an increase in hardness; however, the coarsening process of carbides promoted a decrease in hardness. Nanoindentation tests of the austenite matrix indicated an increase in ductility with increasing aging time.     

Pore structure evolution during the coke graphitization process in a blast furnace

Pore structure is an important factor influencing coke strength, while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace. Therefore, an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace. Coke graphitization was simulated at different heating temperatures from 1100 to 1600℃ at intervals of 100℃. The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method. Results show that the adsorption and desorption curves of graphitized coke have intersection points, and the two curves did not coincide, instead forming a "hysteresis loop." Based on the hysteresis loop analysis, the porous structure of the graphitized coke mostly appeared in the shape of a "hair follicle." Furthermore, with an increase in heating temperature, the apparent porosity, specific surface area, total pore volume, and amount of micropores showed good correlation and can divided into three stages: 1100–1200, 1200–1400, and 1400–1600℃. When the temperature was less than 1400℃, ash migration from the inner part mainly led to changes in the coke pore structure. When the temperature was greater than 1400℃, the pore structure evolution was mainly affected by the coke graphitization degree. The results of scanning electron microscopy, energy dispersive spectrometry, and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400℃ contributed to these changes.     

Direct reduction of iron ore by biomass char

By using thermogravimetric analysis the process and mechanism of iron ore reduced by biomass char were investigated and compared with those reduced by coal and coke. It is found that biomass char has a higher reactivity. The increase of carbon-to-oxygen mole ratio (C/O) can lead to the enhancement of reaction rate and reduction fraction, but cannot change the temperature and trend of each reaction. The reaction temperature of hematite reduced by biomass char is at least 100 K lower than that reduced by coal and coke, the maximum reaction rate is 1.57 times as high as that of coal, and the final reaction fraction is much higher. Model calculation indicates that the use of burden composed of biomass char and iron ore for blast furnaces can probably decrease the temperature of the thermal reserve zone and reduce the CO equilibrium concentration.     

Effect of ash on coal structure and combustibility

Four bituminous coals and one anthracite were used in this study. On the basis of the similar volatile matter contents of the four bituminous coals, the effects of ash in coal on the microstructure, carbonaceous structure, and chemical composition of pulverized coal were studied. Thermogravimetric analysis was used to study the effect of the addition of anthracite on the combustibility of four different bituminous coals. The results showed that with the increase of ash content in pulverized coal, the microstructure of carbon particles in coal was not much different. However, the analysis results of Raman spectroscopy and X-ray diffraction pattern showed that as the ash content increased, the degree of graphitization of coal carbonaceous structure gradually decreased. The combustibility of the four bituminous coals were better than that of the anthracite. When bituminous coal and anthracite were mixed and burned, the combustibility of the mixed sample decreased as the ash content increased.     

Reduction behavior and kinetics of vanadium-titanium sinters under high potential oxygen enriched pulverized coal injection

In this work, the reduction behavior of vanadium-titanium sinters was studied under five different sets of conditions of pulverized coal injection with oxygen enrichment. The modified random pore model was established to analyze the reduction kinetics. The results show that the reduction rate of sinters was accelerated by an increase of CO and H₂ contents. Meanwhile, with the increase in CO and H₂ contents, the increasing range of the medium reduction index (MRE) of sinters decreased. The increasing oxygen enrichment ratio played a diminishing role in improving the reduction behavior of the sinters. The reducing process kinetic parameters were solved using the modified random role model. The results indicated that, with increasing oxygen enrichment, the contents of CO and H₂ in the reducing gas increased. The reduction activation energy of the sinters decreased to between 20.4 and 23.2 kJ/mol.     

Silicon assistant carbothermal reduction for SiC powders

The silicon assistant method to increase the reaction yield of carbothermal reduction of silica at a lower temperature is reported. The effect of silicon on the carbothermal reduction process has been investigated in detail. Compared with traditional reduction, the introduction of silicon can change the reaction path and further increase the conversion of silicon carbide at a lower temperature. It is considered that the assistant reduction consists of three steps: vaporizing and melting of silicon, formation of silicon monoxide, and synthesis of silicon carbide. The morphology of the synthesized SiC powders through the silicon assistant method can be affected apparently by the experimental temperature.     

用焦煤和氧化钙制备含CaO碳球团: 热解炉中温度、孔分布和碳结构对球团抗压强度的影响

CaO-containing carbon pellets (CCCP) were successfully prepared from well-mixed coking coal (CC) and calcium oxide (CaO) and roasted at different pyrolysis temperatures. The effects of temperature, pore distribution, and carbon structure on the compressive strength of CCCP was investigated in a pyrolysis furnace (350–750°C). The results showed that as the roasting temperature increased, the compressive strength also increased and furthermore, structural defects and imperfections in the carbon crystallites were gradually eliminated to form more organized char structures, thus forming high-ordered CC. Notably, the CCCP preheated at 750°C exhibited the highest compressive strength. A positive relationship between the compressive strength and pore-size homogeneity was established. A linear relationship between the compressive strength of the CCCP and the average stack height of CC was observed. Additionally, a four-stage caking mechanism was developed.     

Study of Rotor Spun Basofil/Cotton Blended Yarn Quality Characteristics during Optimisation of Processing Parameters

Yarn quality characteristics are affected by processing parameters. A 36 tex rotor spun yarn of 50/50 Basofil/ cotton （B/C） blended yarn was spun, and the spinning process optimised for rotor speed, opening roller speed and twist factor. Selected yarn characteristics were studied during the optimization process. During the optimizations process yarn elongation and hairiness reduced with increase in rotor speed. Tenacity increased with increase of rotor speed. The increase in TF caused tenacity and CV of count to increase up to a peak and then started to decrease with further increase of TF.While TF caused an increase in yarn hairiness, elongation decreased to a minimum level and then started to increase with further increase of TF. CV of count and hairiness increased with increase in opening roller speed, but tenacity and elongation decreased with increase in opening roller speed. The optimization process yielded the optimum levels for rotor speed, opening roller speed and twist factor （TF） as 45,000 rpm, 6,500 rpm and 450 respectively. As per uster Standards the optimum yam showed good results for CV of count, CV of tenacity and thin places/km.     

Development of calcium coke for CaC_2 production using calcium carbide slag and coking coal

A type of calcium coke was developed for use in the oxy-thermal process of calcium carbide production.The calcium coke was prepared by the co-pyrolysis of coking coal and calcium carbide slag, which is a solid waste generated from the chlor-alkali industry.The characteristics of the calcium cokes under different conditions were analyzed experimentally and theoretically.The results show that the thermal strength of calcium coke increased with the increase in the coking coal proportion, and the waterproof property of calcium coke also increased with increased carbonation time.The calcium coke can increase the contact area of calcium and carbon in the calcium carbide production process.Furthermore, the pore structure of the calcium coke can enhance the diffusion of gas inside the furnace, thus improving the efficiency of the oxy-thermal technology.     

氧热法电石合成的反应平衡和热匹配分析

针对氧热法电石合成中吸热的生成反应和放热的碳燃烧反应耦合,从热力学角度对电石生成途径、反应化学计量平衡以及吸、放热反应热耦合进行了分析。结果表明:(1)电石由CaO+3C→CaC2+CO一步直接生成的可能性更大;(2)不同化学计量对应4种不同反应体系,各体系电石平衡转化率都随温度升高而升高,随压强增大而减小,电石与氧化钙发生副反应的转化率大致为随温度升高而先升后降;(3)反应热匹配量和匹配条件取决于电石生成反应物料处理量和电石纯度要求。电石生成反应与燃烧供热反应耦合于同一反应器是可行的。     

氧热法电石合成淤浆鼓泡床反应器的流动特性

针对氧热法电石合成的电石吸热反应和炭燃烧放热耦合特点,本文设计并研究了适用该过程的三相淤浆鼓泡床反应器。采用空气-水-氯化聚氯乙烯（CPVC）模拟物系,实测了不同表观气速、固体颗粒进料量和静液高度下淤浆鼓泡床床层中局部平均气含率、固含率轴向分布和大、小两类气泡的分布。结果表明表观气速越大,局部平均气含率越大;固体颗粒的加入减小了床层局部平均气含率。当Ug在0.136~0.196m/s之间时,固含率轴向分布随表观气速增大趋于均匀;固体颗粒进料量越小则固含率沿轴向分布越均匀。随着表观气速的增加,小气泡含量逐渐增加,大气泡含量逐渐减小;随着静液高度的增加,大气泡含量均是先增大后减小。上述结果表明电石生成反应与燃烧供热反应原位耦合于淤浆鼓泡床中是可行的。     

电石渣作混合材对水泥结构与性能影响的试验研究

探讨以电石渣作水泥混合材时不同掺量对水泥结构与性能的影响.结果表明:掺入电石渣可使溶液中Ca(OH)2浓度增加,水化反应加快,缩短水泥的凝结时间;电石渣掺量的增加可以减小水泥的比重、提高水泥的比表面积并且水泥安定性合格;掺入适量的电石渣可提高水泥的早期强度;在同一电石渣掺量下,水泥强度随着水灰比的减少而增大.     

废塑料配煤炼焦对焦炭质量的影响

为降低配煤炼焦生产中焦煤用量,提高废塑料利用率,利用废塑料代替一定比例焦煤,在40 kg实验焦炉中与煤共焦化,考察焦炭、焦油产率和焦炭强度的变化规律。结果表明:以质量分数为1%~5%的废塑料替代焦煤炼焦后,焦炭产率下降,焦油产率增加,M25先提高后下降,M10先下降后提高,焦炭的反应性提高,而反应后强度下降;当废塑料质量分数控制在3%以下时,焦炭的冷态强度和热态强度符合国家二级冶金焦炭质量分级标准。该结果为工业生产提供了参考。     

利用铁桶试验预测工业焦炉成焦质量的研究

为优化炼焦炉入炉煤配方以及提高焦炭产品质量,利用20 kg铁桶随炉试验以预测工业焦炉的成焦质量,并建立了预测数学模型。结果表明,利用20 kg铁桶试验可准确预测工业焦炉成焦强度,二者表现出很好的相关性,可直接用于指导工业生产过程中的配煤操作,具有很强的实用性。     

减水剂对掺电石渣水泥强度与结构影响的研究

探讨不同掺量的减水剂对掺电石渣水泥强度与结构的影响.结果表明:当w电石渣掺量为5%时,掺入减水剂会使掺电石渣水泥的早期强度有所下降.当w电石渣掺量大于20%时,掺入减水剂可消除水泥的凝聚现象,大大提高水泥的流动性,降低硬化水泥浆体的孔隙率,明显提高掺电石渣水泥的早期强度,且水灰比越低,减水剂的增强效果越强.本试验中w减水剂的最佳掺量为0.75%.减水剂的掺入对掺电石渣水泥的后期强度影响不大.     

电石渣制备纳米晶碳酸钙的液相法工艺研究

文章研究了以氯化铵为提取液,利用液相法从电石渣中提取钙的工艺条件,并利用提取的钙与碳酸铵反应,成功制备出了纳米碳酸钙;从降低生产成本与提高产品质量出发,设计了一个二级循环浸取工艺,从而成功实现了氯化铵在整个制备过程中的循环利用,并达到环保的目的;该工艺中钙的提取率可达91.43%,产品碳酸钙的纯度与白度分别为99.93%与98,符合国家标准;X射线粉末衍射(XRD)结果表明,产物为纯净的方解石型碳酸钙;透射电子显微镜(TEM)显示产物的粒径为30 nm左右。     

氧热法电石生产气流床反应器性能的数值模拟

针对氧热法电石生产工艺中气流床反应器内的燃烧放热和电石生成的吸放热耦合体系,建立了包含传质、传热和反应的多相反应器模型,基于模拟重点考察了反应器几何参数和操作条件对器内传递和反应性能的影响。结果表明：(1)气体通过气流床中的预热段、扩大段时,温度达到1000K以上,反应段的局部温度达到3000K以上,可以满足原料预热和电石合成需要的温度;(2)焦炭的粒度增大,其火焰中心位置下移,可以更好地为底部电石合成反应提供热量;但是焦炭的粒度增大,气体出口温度变大,能量没有得到充分利用;(3)适宜焦炭粒度为120μm,对合成电石和减小能耗有利。